But Bosch has taken Musk's concept a step further, turning twin Tesla Model S sedans into truly self-driving vehicles that my company recently had the chance to sample at a track in Germany. But like most fully automated driving technology, we can't expect to see cars like this on roads soon for several reasons, one of which is cost.

Bosch self-driving Tesla Model S. Photo by Bosch.

Bosch spent an estimated $225,000 to retrofit the two Teslas, which cost about $90,000 each. This included roughly 1,400 man hours to add about 50 Bosch components and nearly a mile of cabling to tie them all together. The components included several off-the-shelf sensors, such as front stereo video cameras (SVCs) to identify road markings, signs and obstacles, and are the smallest SVCs on the market, according to Bosch.

The cars were also equipped with forward- and rear-facing long-range and mid-range radar sensors, inertial sensors, backup braking and electronic control unit (ECU) systems and a custom computer in the rear trunk that runs proprietary high-resolution mapping and operating system software. The only non-Bosch sensors used are Velodyne lidar scanners that can "see" 360 degrees around the car, but are mounted behind panels so that the exterior of the Model S looks almost stock except for a subtle GPS antenna on the back. The interior is a bit more mad scientist, with a screen added to the dash that shows a sensor-eye view of the road ahead as well as the car's surroundings.

We rode in the autonomous Model S at the Bosch test track in Boxberg, Germany, following a Ford Fiesta pilot car to show how the technology can react to everyday situations. While we sat in the front passenger seat, a Bosch engineer in the driver's seat – with hands off the wheel and feet off the pedals – demonstrated how the car could stop suddenly on its own in reaction to the Fiesta and also crawl as if in bumper-to-bumper traffic. It could also accelerate up to about 50 mph without the Fiesta in front. The Teslas can also swap lanes, pass other vehicles and even merge into traffic via on ramps and off ramps, although that wasn't part of our test drive.

Bosch's self-driving technology can also reach speeds of up to about 80 mph, and has achieved those speeds on public roads. Bosch began testing automated driving on public roads in 2013, using modified BMW 325d Touring sedans. The company said that "engineers have successfully driven them for several thousand kilometers on freeways – both the A81 near Stuttgart and the I-280 in California."

One of the reasons Bosch built twin self-driving Model S's is that it has two teams – one at the company's Abstatt facility in Germany and another in Palo Alto, California – working on autonomous driving technology. Having identical platforms makes "it as easy as possible for the two teams to share their results," Bosch said. On why the Telsa Model S was chosen, Dr. Dirk Hoheisel, member of the Bosch board of management, said “they combine two automotive industry trends: electrification and automation.” Plus, they're just cool cars.

And while a fully self-driving Model S may be out of reach of most car buyers, Bosch said it hopes to bring autonomous technology to the masses by refining the sensors, reducing the size of the PC to a compact ECU and essentially making the technology as common as cruise control today. While like most automakers and suppliers the company is using the milestone of the year 2020 as when we could see self-driving cars on the market, it acknowledged that there are other hurdles beside price to overcome.

One is liability and who is responsible when a self-driving car crashes. Another related issue is legislation, while a third is mapping data. Bosch devised its own high-resolution maps for the specific routes the cars drive, but acknowledged that map data will need to improve before fully autonomous technology is ready for prime time, with more information coming from outside the car in the form of vehicle-to-vehicle and vehicle-to-infrastructure communication and "smart" transportation infrastructure.

While a fully self-driving Tesla Model S is out of reach for now – and there's always Auto Pilot – our time with Bosch in Germany convinced us that it's only a matter of time before we'll be able to let go of the wheel when we want. But also drive ourselves when we want, and in the future, have the best of both worlds.